Home Network – Wired – Wireless

Hi,
I have a network of 2 pc at home (one connected via cable to the router and a laptop is connected via wireless to the router) connected to a Linksys WRT54G Router.

The problem is to transfer files between computers;
When i try to transfer a file the system tells me that the network path is not accessable availble but if i connect the laptop via wire instead of a wireless connection everything works perfectly without doing any settings.

Please note the follwoing;
The internet works good
i have no firewall active
about a month ago everything was working perfectly.

can anyone help please?

sandro